Many electronic and mechanical devices have performance limitations that relate to a maximum allowable temperature of operation. It is known in integrated circuit devices (“ICs”) that higher system cycle rates result in increased system performance, but they also result in increased heating of the IC device. This heating may be an issue in some applications, because it results in decreased reliability and decreased IC lifetime. It is known to attach high thermally conductive materials to ICs to form improved heat-dissipation structures, generally known as heat sinks, in order to increase the performance rate of the IC without exceeding the thermal limitation. In the case of an IC, the junction temperature may be the thermal limit. This thermal issue may be very serious in certain applications, since operating an IC at a rate that causes the junction temperature to exceed the allowed limit for the particular technology, results in a greatly decreased IC lifetime. There may be a typically exponential decrease in lifetime as a function of small linear increases in junction temperature for many types of ICs, as well as for many other systems such as electric motors.
The use of heat-dissipating devices improves the thermal limitation capability in ICs and in other electronic devices, by reducing the temperature difference between the outside ambient temperature and the junction area deep within the IC. This may be known as the junction to ambient temperature difference θJA. Even though the performance rate of an IC can be increased without exceeding the junction temperature thermal limit by means of a heat-dissipating device, there may still be a need to increase the performance rate to as high a level as possible. In addition, the use of heat-dissipation structures is expensive, adds yet another component subject to failure to the overall system, adds another step to the assembly process, may require mechanical devices such as fans be added to the system, and may take up more space than may be allowed in personal electronic devices.
Thus there is a need to find methods and apparatus to control the performance rate of an electronic device to a performance level that is as high as it can be, but without exceeding the thermal limitation. This need exists in electronic devices such as ICs that cannot practically employ heat dissipation structures, and in ICs that use heat-dissipation structures but need to optimize their performance rate to the best possible rate in order to obtain a competitive edge in the market. The need to control and optimize the performance rate exists in electrical systems as well as in electronic devices, for example a power transformer. The need to control and optimize the performance rate may also exist in mechanical systems as well as electrical systems, such as a motor operating an electrical generator. Any system that has a thermal limitation that relates to a controllable performance value may need to optimize its performance under various demand levels, while not exceeding the thermal limitation at any time.